perf machine: Add machine__get_kallsyms_filename()

Separate out the logic used to make the kallsyms full path name for a
machine.  It will be reused in a subsequent patch.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1391004884-10334-4-git-send-email-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/machine.c

@@ -496,19 +496,22 @@ static int symbol__in_kernel(void *arg, const char *name,
 	return 1;
 }
 
+static void machine__get_kallsyms_filename(struct machine *machine, char *buf,
+					   size_t bufsz)
+{
+	if (machine__is_default_guest(machine))
+		scnprintf(buf, bufsz, "%s", symbol_conf.default_guest_kallsyms);
+	else
+		scnprintf(buf, bufsz, "%s/proc/kallsyms", machine->root_dir);
+}
+
 /* Figure out the start address of kernel map from /proc/kallsyms */
 static u64 machine__get_kernel_start_addr(struct machine *machine)
 {
-	const char *filename;
-	char path[PATH_MAX];
+	char filename[PATH_MAX];
 	struct process_args args;
 
-	if (machine__is_default_guest(machine))
-		filename = (char *)symbol_conf.default_guest_kallsyms;
-	else {
-		sprintf(path, "%s/proc/kallsyms", machine->root_dir);
-		filename = path;
-	}
+	machine__get_kallsyms_filename(machine, filename, PATH_MAX);
 
 	if (symbol__restricted_filename(filename, "/proc/kallsyms"))
 		return 0;